feat: add AGC to capture + playout paths, add server UI, DNS resolve

- Wire AutoGainControl on both capture (mic → encode) and playout
  (decode → speaker) paths to normalize volume levels
- Add server list with add/remove custom server dialog
- Add IPv4/IPv6 preference toggle for DNS resolution
- Resolve DNS hostnames to IP in Kotlin before passing to Rust engine
- Revert to IP addresses for default servers (DNS still broken on QUIC)

AGC confirmed working — voice levels noticeably improved in testing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

android/app/src/main/java/com/wzp/ui/call/CallViewModel.kt

@@ -14,6 +14,11 @@ import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
+import java.net.Inet4Address
+import java.net.Inet6Address
+import java.net.InetAddress
+
+data class ServerEntry(val address: String, val label: String)
 
 class CallViewModel : ViewModel(), WzpCallback {
 
@@ -45,15 +50,21 @@ class CallViewModel : ViewModel(), WzpCallback {
     private val _roomName = MutableStateFlow(DEFAULT_ROOM)
     val roomName: StateFlow<String> = _roomName.asStateFlow()
 
-    private val _selectedServer = MutableStateFlow(0) // index into SERVERS
+    private val _selectedServer = MutableStateFlow(0)
     val selectedServer: StateFlow<Int> = _selectedServer.asStateFlow()
 
+    private val _servers = MutableStateFlow(DEFAULT_SERVERS.toList())
+    val servers: StateFlow<List<ServerEntry>> = _servers.asStateFlow()
+
+    private val _preferIPv6 = MutableStateFlow(false)
+    val preferIPv6: StateFlow<Boolean> = _preferIPv6.asStateFlow()
+
     private var statsJob: Job? = null
 
     companion object {
-        val SERVERS = listOf(
+        val DEFAULT_SERVERS = listOf(
-            "172.16.81.175:4433" to "LAN (172.16.81.175)",
+            ServerEntry("172.16.81.175:4433", "LAN (172.16.81.175)"),
-            "pangolin.manko.yoga:4433" to "Pangolin (remote)",
+            ServerEntry("193.180.213.68:4433", "Pangolin (IP)"),
         )
         const val DEFAULT_ROOM = "android"
     }
@@ -70,15 +81,70 @@ class CallViewModel : ViewModel(), WzpCallback {
     }
 
     fun selectServer(index: Int) {
-        if (index in SERVERS.indices) {
+        if (index in _servers.value.indices) {
             _selectedServer.value = index
         }
     }
 
+    fun setPreferIPv6(prefer: Boolean) { _preferIPv6.value = prefer }
+
+    fun addServer(hostPort: String, label: String) {
+        val current = _servers.value.toMutableList()
+        current.add(ServerEntry(hostPort, label))
+        _servers.value = current
+    }
+
+    fun removeServer(index: Int) {
+        if (index < DEFAULT_SERVERS.size) return // don't remove built-in servers
+        val current = _servers.value.toMutableList()
+        if (index in current.indices) {
+            current.removeAt(index)
+            _servers.value = current
+            if (_selectedServer.value >= current.size) {
+                _selectedServer.value = 0
+            }
+        }
+    }
+
     fun setRoomName(name: String) { _roomName.value = name }
 
+    /**
+     * Resolve DNS hostname to IP address on the Kotlin/Android side,
+     * since Rust's DNS resolution may not work on Android.
+     * Returns "ip:port" string.
+     */
+    private fun resolveToIp(hostPort: String): String {
+        val parts = hostPort.split(":")
+        if (parts.size != 2) return hostPort
+        val host = parts[0]
+        val port = parts[1]
+
+        // Already an IP address — return as-is
+        if (host.matches(Regex("""\d+\.\d+\.\d+\.\d+"""))) return hostPort
+        if (host.contains(":")) return hostPort // IPv6 literal
+
+        return try {
+            val addresses = InetAddress.getAllByName(host)
+            val preferV6 = _preferIPv6.value
+            val picked = if (preferV6) {
+                addresses.firstOrNull { it is Inet6Address } ?: addresses.firstOrNull { it is Inet4Address }
+            } else {
+                addresses.firstOrNull { it is Inet4Address } ?: addresses.firstOrNull { it is Inet6Address }
+            }
+            if (picked != null) {
+                val ip = picked.hostAddress ?: host
+                val formatted = if (picked is Inet6Address) "[$ip]:$port" else "$ip:$port"
+                formatted
+            } else {
+                hostPort
+            }
+        } catch (_: Exception) {
+            hostPort // resolution failed — pass through and let Rust try
+        }
+    }
+
     fun startCall() {
-        val relay = SERVERS[_selectedServer.value].first
+        val serverEntry = _servers.value[_selectedServer.value]
         val room = _roomName.value
         try {
             if (engine == null) {
@@ -89,11 +155,13 @@ class CallViewModel : ViewModel(), WzpCallback {
                 engineInitialized = true
             }
             _callState.value = 1
+            _errorMessage.value = null
             acquireWakeLocks?.invoke()
             startStatsPolling()
 
             viewModelScope.launch(kotlinx.coroutines.Dispatchers.IO) {
                 try {
+                    val relay = resolveToIp(serverEntry.address)
                     val result = engine?.startCall(relay, room) ?: -1
                     if (result != 0) {
                         _callState.value = 0

android/app/src/main/java/com/wzp/ui/call/InCallScreen.kt

@@ -4,6 +4,8 @@ import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.ExperimentalLayoutApi
+import androidx.compose.foundation.layout.FlowRow
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxSize
@@ -12,8 +14,11 @@ import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.AlertDialog
 import androidx.compose.material3.Button
 import androidx.compose.material3.ButtonDefaults
 import androidx.compose.material3.FilledIconButton
@@ -21,12 +26,18 @@ import androidx.compose.material3.FilledTonalIconButton
 import androidx.compose.material3.IconButtonDefaults
 import androidx.compose.material3.LinearProgressIndicator
 import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedButton
 import androidx.compose.material3.OutlinedTextField
 import androidx.compose.material3.Surface
+import androidx.compose.material3.Switch
 import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
@@ -38,6 +49,7 @@ import androidx.compose.ui.unit.sp
 import com.wzp.engine.CallStats
 import kotlin.math.roundToInt
 
+@OptIn(ExperimentalLayoutApi::class)
 @Composable
 fun InCallScreen(
     viewModel: CallViewModel,
@@ -51,6 +63,10 @@ fun InCallScreen(
     val errorMessage by viewModel.errorMessage.collectAsState()
     val roomName by viewModel.roomName.collectAsState()
     val selectedServer by viewModel.selectedServer.collectAsState()
+    val servers by viewModel.servers.collectAsState()
+    val preferIPv6 by viewModel.preferIPv6.collectAsState()
+
+    var showAddServerDialog by remember { mutableStateOf(false) }
 
     Surface(
         modifier = Modifier.fillMaxSize(),
@@ -59,12 +75,12 @@ fun InCallScreen(
         Column(
             modifier = Modifier
                 .fillMaxSize()
-                .padding(24.dp),
+                .padding(24.dp)
+                .verticalScroll(rememberScrollState()),
             horizontalAlignment = Alignment.CenterHorizontally
         ) {
             Spacer(modifier = Modifier.height(48.dp))
 
-            // App title
             Text(
                 text = "WZ Phone",
                 style = MaterialTheme.typography.headlineMedium.copy(
@@ -78,8 +94,7 @@ fun InCallScreen(
             CallStateLabel(callState)
 
             if (callState == 0) {
-                // Idle — show connect button
+                Spacer(modifier = Modifier.height(32.dp))
-                Spacer(modifier = Modifier.height(48.dp))
 
                 // Server selector
                 Text(
@@ -88,16 +103,16 @@ fun InCallScreen(
                     color = MaterialTheme.colorScheme.onSurfaceVariant
                 )
                 Spacer(modifier = Modifier.height(4.dp))
-                Row(
+                FlowRow(
                     modifier = Modifier.fillMaxWidth(),
                     horizontalArrangement = Arrangement.Center
                 ) {
-                    CallViewModel.SERVERS.forEachIndexed { idx, (_, label) ->
+                    servers.forEachIndexed { idx, entry ->
                         val isSelected = selectedServer == idx
                         FilledTonalIconButton(
                             onClick = { viewModel.selectServer(idx) },
                             modifier = Modifier
-                                .padding(horizontal = 4.dp)
+                                .padding(2.dp)
                                 .height(36.dp)
                                 .width(140.dp),
                             shape = RoundedCornerShape(8.dp),
@@ -111,13 +126,56 @@ fun InCallScreen(
                             }
                         ) {
                             Text(
-                                text = label,
+                                text = entry.label,
                                 style = MaterialTheme.typography.labelSmall,
                                 maxLines = 1
                             )
                         }
                     }
+                    // + Add button
+                    OutlinedButton(
+                        onClick = { showAddServerDialog = true },
+                        modifier = Modifier
+                            .padding(2.dp)
+                            .height(36.dp),
+                        shape = RoundedCornerShape(8.dp)
+                    ) {
+                        Text("+", style = MaterialTheme.typography.labelMedium)
                     }
+                }
+
+                // IPv4/IPv6 preference
+                Spacer(modifier = Modifier.height(8.dp))
+                Row(
+                    verticalAlignment = Alignment.CenterVertically,
+                    horizontalArrangement = Arrangement.Center
+                ) {
+                    Text(
+                        text = "IPv4",
+                        style = MaterialTheme.typography.labelSmall,
+                        color = if (!preferIPv6) MaterialTheme.colorScheme.primary
+                               else MaterialTheme.colorScheme.onSurfaceVariant
+                    )
+                    Switch(
+                        checked = preferIPv6,
+                        onCheckedChange = { viewModel.setPreferIPv6(it) },
+                        modifier = Modifier.padding(horizontal = 8.dp)
+                    )
+                    Text(
+                        text = "IPv6",
+                        style = MaterialTheme.typography.labelSmall,
+                        color = if (preferIPv6) MaterialTheme.colorScheme.primary
+                               else MaterialTheme.colorScheme.onSurfaceVariant
+                    )
+                }
+
+                // Selected server address
+                Spacer(modifier = Modifier.height(4.dp))
+                Text(
+                    text = servers.getOrNull(selectedServer)?.address ?: "",
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant
+                )
 
                 Spacer(modifier = Modifier.height(8.dp))
                 OutlinedTextField(
@@ -149,7 +207,6 @@ fun InCallScreen(
                     )
                 }
 
-                // Show error if any
                 errorMessage?.let { err ->
                     Spacer(modifier = Modifier.height(16.dp))
                     Text(
@@ -172,7 +229,7 @@ fun InCallScreen(
 
                 AudioLevelBar(stats.audioLevel)
 
-                Spacer(modifier = Modifier.weight(1f))
+                Spacer(modifier = Modifier.height(48.dp))
 
                 ControlRow(
                     isMuted = isMuted,
@@ -181,7 +238,6 @@ fun InCallScreen(
                     onToggleSpeaker = viewModel::toggleSpeaker,
                     onHangUp = {
                         viewModel.stopCall()
-                        // Don't finish activity — go back to idle
                     }
                 )
 
@@ -193,6 +249,71 @@ fun InCallScreen(
             }
         }
     }
+
+    if (showAddServerDialog) {
+        AddServerDialog(
+            onDismiss = { showAddServerDialog = false },
+            onAdd = { host, port, label ->
+                viewModel.addServer("$host:$port", label)
+                showAddServerDialog = false
+            }
+        )
+    }
+}
+
+@Composable
+private fun AddServerDialog(
+    onDismiss: () -> Unit,
+    onAdd: (host: String, port: String, label: String) -> Unit
+) {
+    var host by remember { mutableStateOf("") }
+    var port by remember { mutableStateOf("4433") }
+    var label by remember { mutableStateOf("") }
+
+    AlertDialog(
+        onDismissRequest = onDismiss,
+        title = { Text("Add Server") },
+        text = {
+            Column {
+                OutlinedTextField(
+                    value = host,
+                    onValueChange = { host = it },
+                    label = { Text("Host (IP or domain)") },
+                    singleLine = true,
+                    modifier = Modifier.fillMaxWidth()
+                )
+                Spacer(modifier = Modifier.height(8.dp))
+                OutlinedTextField(
+                    value = port,
+                    onValueChange = { port = it },
+                    label = { Text("Port") },
+                    singleLine = true,
+                    modifier = Modifier.fillMaxWidth()
+                )
+                Spacer(modifier = Modifier.height(8.dp))
+                OutlinedTextField(
+                    value = label,
+                    onValueChange = { label = it },
+                    label = { Text("Label (optional)") },
+                    singleLine = true,
+                    modifier = Modifier.fillMaxWidth()
+                )
+            }
+        },
+        confirmButton = {
+            TextButton(
+                onClick = {
+                    if (host.isNotBlank()) {
+                        val displayLabel = label.ifBlank { host }
+                        onAdd(host.trim(), port.trim(), displayLabel)
+                    }
+                }
+            ) { Text("Add") }
+        },
+        dismissButton = {
+            TextButton(onClick = onDismiss) { Text("Cancel") }
+        }
+    )
 }
 
 @Composable
@@ -261,8 +382,6 @@ private fun QualityIndicator(tier: Int, label: String) {
 
 @Composable
 private fun AudioLevelBar(audioLevel: Int) {
-    // audioLevel is RMS of i16 samples (0-32767).
-    // Map to 0.0-1.0 with a log-ish curve for better visual feel.
     val level = if (audioLevel > 0) {
         (audioLevel.toFloat() / 8000f).coerceIn(0.02f, 1f)
     } else {

crates/wzp-android/src/engine.rs

@@ -15,6 +15,7 @@ use std::time::Instant;
 
 use bytes::Bytes;
 use tracing::{error, info, warn};
+use wzp_codec::agc::AutoGainControl;
 use wzp_codec::opus_dec::OpusDecoder;
 use wzp_codec::opus_enc::OpusEncoder;
 use wzp_crypto::{KeyExchange, WarzoneKeyExchange};
@@ -275,10 +276,14 @@ async fn run_call(
     let mut fec_enc = wzp_fec::create_encoder(&profile);
     let mut fec_dec = wzp_fec::create_decoder(&profile);
 
+    // AGC: normalize volume on both capture and playout paths
+    let mut capture_agc = AutoGainControl::new();
+    let mut playout_agc = AutoGainControl::new();
+
     info!(
         fec_ratio = profile.fec_ratio,
         frames_per_block = profile.frames_per_block,
-        "codec + FEC initialized (48kHz mono, 20ms frames, RaptorQ)"
+        "codec + FEC + AGC initialized (48kHz mono, 20ms frames)"
     );
 
     let seq = AtomicU16::new(0);
@@ -310,6 +315,9 @@ async fn run_call(
                 continue;
             }
 
+            // AGC: normalize capture volume before encoding
+            capture_agc.process_frame(&mut capture_buf);
+
             // Opus encode
             let encoded_len = match encoder.encode(&capture_buf, &mut encode_buf) {
                 Ok(n) => n,
@@ -440,12 +448,15 @@ async fn run_call(
                     if !is_repair {
                         match decoder.decode(&pkt.payload, &mut decode_buf) {
                             Ok(samples) => {
+                                // AGC on playout — normalizes received audio volume
+                                playout_agc.process_frame(&mut decode_buf[..samples]);
                                 state.playout_ring.write(&decode_buf[..samples]);
                                 frames_decoded += 1;
                             }
                             Err(e) => {
                                 warn!("opus decode error: {e}");
                                 if let Ok(samples) = decoder.decode_lost(&mut decode_buf) {
+                                    playout_agc.process_frame(&mut decode_buf[..samples]);
                                     state.playout_ring.write(&decode_buf[..samples]);
                                 }
                             }